Patent GB-516197-A (GB)
Title: Improvements relating to fusible electric cut-outs
IPC: H01H85/28
Filed: 1938-07-14
Abstract: 516,197. Fusible cut-outs. BRITISH THOMSON-HOUSTON CO., Ltd. July 14, 1938, No. 20920. Convention date, July 14, 1937. [Class 38 (i)] A pair of fuses 20, 21 are mounted on a door 55 of a casing, the upper end caps 22, 23 of both fuses being connected to contact blades 17, 18, 19, and the lower ends of the fuses being anchored by fuse link extensions 24, 25 to terminals so mounted that one of the fuses is in circuit and when blown releases a switch that puts the other fuse in circuit and allows the lower end of the door to move outwards to indicate the condition of the fuse. When the second fuse blows the cap 22 is released from the blades 17, 18, 19 by a downward movement allowing the door 55 to fall open both fuse holders 20, 21 remaining attached to the door and fixed relatively to one another. In one construction, Fig. 1, the fuse holders 20 and 21 are mounted in a supporting element 26 which is pivoted to the door 55 of the cut-out casing at 28. The contact caps 22 and 23 at the upper ends of the holders are interconnected by a clamping bar 61 provided with clip arms 66 and a resilient spacing element 67. The bent end 63 is removably secured under a strap 62 on the door 55. Contact cap 22, is held by a pair of resilient contact fingers 19 and the supporting element 26 engages a lever element 30, which can rotate about a hinge bracket 15, by means of pins 27 and 35, which project into triangular openings 37 in the arms 34 of the lever element. The fuse 'link extension 24 in the holder 20 passes round a projection 44 on the lever 30 and is secured to a terminal 43. An arm 46 pivoted to the lever 30 is pressed against the contact 13 to complete the circuit to the contact 13. When the fuse link 24 is released by the blowing of the fuse 20 the lever 30 turns about the pivot 32 to an extent limited by the engagement of the pins 35 with the sides of the openings 37 and pins 50 resting on arms 51, the movement being effected by the spring pressing'the lever 46 against the contact 13. This contact is not broken and switch arms 70 are raised into engagement with blades 76 to put the second fuse 21 into circuit. The release of the arms 70 is delayed by an escapement 80, 86. When the second fuse blows a spring 94 moves the arms 51 from under the pins 50 and allows the release of the cap 22 from the blades 17, 18, 19. In a simplified form, Figs. 22 to 25 (not shown), the putting of the second fuse into circuit is effected by a lever pivoted to the member 30 engaging a hook contact on the second fuse acting also as a detent which is released when the second fuse blows. In other modifications a dash pot or spring bellows affords the means for delaying the switch action and the switch contacts have a rectilinear motion. The release of the switch mechanism is in one case effected by a projection on the sliding contact bar being freed by the withdrawal of a detent on the lever 30, Figs 10 to 13 (not shown) or by the movement of the cover 55, in which the spring bellows mechanism is mounted, withdrawing a lever from restraint by the casing 10, Figs. 5 to 8 (not shown). In a further modification, Figs. 14 to 21 (not shown), the outer fuse 21 blows first releasing the anchorage of the cover thereto so that the cover is pressed away at the bottom by a spring, and spring-operated switch arms carried by the outer fuse holder are released by an escapement mechanism and engage the lever 30 to complete the circuit through the fuse 20.